Envelopes and the like with remoistenable adhesive comprising polyvinyl alcohol



Al1g- 27, 1957 s. K. BOYAJIAN ENVELOPES AND THE LIKE WITH REMOISTENBLE ADHESIVE COMPRISING POLYVINYL ALCOHOL Filed Sept. 4, 1955 ini INVENTOR.

nited States @arent ENV ELOPES AND THE LIKE WITH REMISTEN- gLllADHESIVE COMPRISING POLYVINY L AL- Setrak K. Boyajian, Worcester, Mass.

Application September 4, 1953, Serial No. 378,683

Claims. (Cl. 117-44) My invention relates to envelopes having remoistenable gummed seal flaps, gummed paper, postage stamps, labels, and the like. y

Hitherto, envelope seal gum has, almost exclusively, consisted of dextrin, in its numerous modifications, by itself in water, or in mixture with acids, alkalies, solvents, and plasticizers, according to the kind of paper it was designed to stick. But dextrin by itself forms, upon drying from its watery solution, a very brittle and distorted film which soon begins to check and crack, and lose much of its adhesive properties even for very soft and easy to stick papers; and when mixed with, or reacted upon by, the materials and chemicals above mentioned, it will, while freeing itself from some of the foregoing objections, acquire thereby numerous other objectionabletfeatures, such as discoloring the paper and giving the gum an unwholesome taste, so that, before my invention, the envelope industry had openly recognized the fact that a fully satisfactory envelope seal gum did not exist, particularly for the sticking of harder papers, such as bond, kraft, etc.

One object of my invention is to provide an envelope seal flap that is free of all the materially objectionable features of hitherto produced envelope seal flaps.

A second object of my invention is to provide an envelope seal iiap that will firmly and permanently stick all grades of envelope paper, Whether soft or hard, including bond, kraft, linen and others of greater or lesser hardness, without the aid of acids, alkalies, or solvents.

A third object of my invention is to provide an envelope seal ap that is free of any odor, and one that possesses a wholesome, pleasant taste.

A fourth object of my invention is to provide an envelope seal ap that is non-checking, non-cracking, and non-curling, and one that will lie smoothly flat, while unsealed, over the body of the envelope without the aid of any chemical plasticizers.

A fifth object of my invention is to provide an envelope seal ap that is materially colorless permanently, and one that will not materially stain or discolor regardless of the kind of paper used in making the envelope.

A sixth object of my invention is to provide an envelope seal iiap that is highly resistant to, and is not materially affected by, atmospheric conditions, such as high humidity and extreme dryness, and one that is materially non-blocking; also an envelope seal flap that will, after `it has been sealed down, neither Wet-out by atmospheric moisture and come open, nor dry-out by extreme atmospheric dryness and also come open, but will remain firmly stuck under all climatic conditions.

A seventh object of my invention is to vprovide an envelope seal flap that will not materially lick-out or washout in remoistening, and one that will not materially clog the wetting blade or wetting brush of the envelope sealing machine.

An eighth object of my invention is to provide an envelope seal ap that will adhere down quickly upon being remoistened and closed down.

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A ninth object of my invention is to providel an en# velope seal gum that will run clean on the applicable envelope machines as they now exist, or as may be designed and developed in the future.

^ Atenth object of my invention is to provide an envelope seal iiap which possesses a combination of all the properties enumerated in the foregoing objects, together with other desirable properties incidental thereto and coexistant therewith; an envelope seal flap so combining these properties having been only a wishful thinking on the part of the envelope industry, never having been achieved before my invention. s

An eleventh object of my invention is to provide an envelope seal gum which is, its higher qualities notwithstanding, economical because it will give greater mileage, requiring both a thinner and narrower film for highly effective sticking. Other objects of my invention will appear hereinafter.

Referring to the drawings, Figures l and 2, respectively, illustrate open-end and open-side envelopes of the conventional design, showing the seal aps having on the marginal portions thereof a layer of remoistenable adhesive coating composition having as its essential ingredient polyvinyl alcohol, as shown at 1, and 1, and yas it is described hereinafter.

With the above-enumerated objects as the goal, it was long since found by this applicant that sources other than dextrin or other 4starch gums must-be brought into use for the production of a completely satisfactory envelope sealv gum. A water soluble plastic with a high tensile strength and structural stability seemed to be the answer, and polyvinyl alcohol appeared to be the most, promising material for the purpose. But polyvinyl alcohol, even in its most advanced methods of production, is not a suliciently pure product in its raw state so that it may be employed as an envelope seal gum: for, while given types of polyvinyl alcohol have been offered as remoistenable adhesive, this applicant has found that even extremely small quantities of contaminants will have a very decisive inuence upon the permanence of the remoistenability of such adhesives, and even if this condition is permissible for some uses, an envelope yseal is not one of them, for if the seal aps of a lot of envelopes become non-remoistenable as time passes, then it becomes so much scrap paper, unless the seal flaps can be regummed, at an almost prohibitive expense, and the envelopes sold aS seconds at greatly reduced prices.

It was, at the time, believed that if the permanence of remoistenability could be assured, a selected grade 0f remoistenable polyvinyl alcohol could satisfy the need for a long sought-after completely suited envelope seal gum, as it seemed to possess all of the remaining properties needed for the purpose. It was also believed that the said selected grade could be made into a permanently remoistenable envelope seal ,gum if it was freed from the` aforementioned contaminants. Consequently, all efforts were focused in that direction for the time being.

But when, after an exhaustive investigation, the desired purity of the selected remoistenable polyvinyl alcohol was obtained, it was found that the resultant gum,

while a decided improvement over the hitherto existingv envelope seal gums, fell somewhat short of achieving the full combination of the objects hereinbefore enumerated. For example, while, when purified the remoistenability was made more permanent, the resultant gum showed considerable operating unstability, varying from lot to lot of the raw product, and even from batch to batch of the water solution from the same lot of the raw product-in tack, in running and sticking properties, in viscosity, etc.

Yet with all these, remoistenable polyvinyl alcohol still` 3 held the biggest promise for an ideal envelope seal gum. Its lack of operating stability as well as uniformity was the first drawback to be overcome. It was then found that while .the selected remoistenable polyvinyl .alcohol as .such did Anot ,whollycombine all ,ofthelproperties ldesired, foran idealenvelope sealgum, some-of its. modifications, chemical or physical, wouldidoso.l

Chemically, hitherto starch, Idextrin, and casein have been suggested as' extenders, and'glycerin` and; glycolsas i variety of hardtostick, color` sensitive, papers. 'It must, t

for example, possess `sufficient tack, but must not materially .cottonor string vin operation,.and `possess all ofthe propertiesfsuggested inthe objects hereinabove. These ends,'I found, could be ybest realized with a product of extreme structural simplicity and integrity. It was then lfound -that these properties could beV obtained by selecting cane sugar as the chemical vmodifier andbo'iling, in aqueous solution, as the physical modifier.

For example, one hundred pounds of dry remoistenablepolyvinyl alcohol of .approximately eightcps. viscosity and one hundred and thirty saponification number is dissolved in three hundred and fifty pounds of hot waterin a suitable jacketed kettle, with amoderately low-speed mixer, and the temperature is brought` up `to slow boilinggand kept there under slow vagitation for approximately `one hour, and as long thereafter `as needed for thecornplete .disappearance yof all the lumps, if any, anda uniform solution results, with all .the volatile impurities distilled oil therefrom. Thereupon one hundred pounds of granulated cane sugar is gradnallyadded and 4` f degrees C. jell on cooling, when such solution is brought to actual boiling and kept there for one hour or more, under agitation, so as to'distill off all of its volatile contaminants, and precipitate all of its solid contaminants, while also breaking up the nesting or clustering of molecules or particles, a near clear, free-flowing, and viscous solution will, after settling out and cooling, result. Such f boiling `will `giyeto polyvinyl alcohol a lustrous, strt1c digested, in the batch and 4the temperature is brought to twohundred degrees F., or slightly under, and kept there for about ten minutes; then the heater and the mixer are turned off.

Where the desired structural simplicity, integrity, and workability of the polyvinyl alcohol solution isv obtained by the boiling alone, then cane sugar may be omitted.

It must bef remembered that the foregoing procedures and formulas are only examples,`and admit wide degrees of variations, polyvinyl alcohol in Veach case being an essential ingredient, and admit further additions.

The envelope seal gumherein described is also ideal for lcoating paper, 4as wellas gummed labels, postage stamps, and gummed tapes.

Various. grades and brands of polyvinyl alcohol differ so widely inl their inherent properties that often there appears nothing common among them other than the name. 4This difference often occurs `even among the various lots of the same brand and grade, though in a lesser degree. The difference is more often physical than chemical. The former is chiefly structural; the latter is largely in the nature and quantity of the contaminants. The Want of `uniformity may or may not be important depending upon the use theypolyvinyl alcohol is to be put to. For the purpose of this invention uniformity is critical. Published descriptive data, often dealing with a single sample, have at times furnished false leads for specialized objective investigation. Forl example, duringmy. investigations in the interest of this Vinvention lV was frequently reminded by such descriptive data Vthat when subjected tto boiling 4temperatures an aqueous solution of polyvinyl alcohol. would `jell upon cooling. I found that while some samples of polyvinyl alcohol lin 22.5%Jinitial: `aqueous vsolution .would if heatedA to 11.00

turally stabilized, integrated, homogenized, quickeradherent upon remoistening, non-jelling and freefowing while in solution, more resistant to humidity, more responsive to applied `moisture, smoother, clearer, and more flexible film-forming, and Vquicker-drying character. Such boiling will not only provide uniformity among various lots of the' same brandand grade of polyvinyl alcohol so as to give its solution a high degree of workability, even without the addition ofcane sugar, but will `also narrow down the hereinbefore mentioned barriers among its various brands and grades., After the first hour of prolonged boiling, there are varying degreesof increase in the tensile strength of the dry film `of polyvinyl'alcohol-thereafter, there'is no notable change. This increase is perhaps due to molecular, particular, and/ or structural integration.

I claim:

`l. An envelope having on the underside of thev marginal portions of the seal flap l.thereof la glossy layer Aof rer'noistenable adhesive coating composition havingas its essential `ingredient polyvinyl alcohol, said layer being non-curling, non-blocking, non-staining, non-checking, and permanently responsive to applied moisture atany temperature, and having a wholesome, pleasant taste, and quick adherence upon remoistening and which has been deposited, from homogeneous free flowing solution.

2. An envelope having on the underside ofthe marginal portions of the` seal flap thereof a glossyilayer of remoistenable adhesive coating compositionhavingas its essential ingredient polyvinyl alcoholA which has been boiledin aqueous solution for approximately one hour. and luntil all the lumps have disappeared and a near-clear homogeneous solution has been formed, with all volatile contaminants distilled off therefrom.

3.1An envelope havingon the underside of the marginal portions of theseal flap thereof a glossy layer of Vremoistenable adhesive coating composition having yas its essen- `tial ingredient polyvinyl-alcoholwhich .has been boiled in aqueous solution for a time sufficient to give it a lustrous, `structurally stabilized, integrated, homogenized, quicker adherent, non-jelling and free-owing while` in cooled solution, more resistant ytohumidity, more responsive to applied moisture, clearer, smoother, stronger, `and more flexible film-forming, and quicker-drying,` character. 4. -An envelope having on the underside of the marginal portions of the seal flap thereof a glossy layer of remois tenable adhesive coating composition having as its essential ingredient polyvinyl alcohol which has been boiled `in' aqueous solution by dissolving in hot water ina suit- .polyvinyl alcohol at theV conclusion of said boiling.

6. As an article of manufacture, paperhaving on one side thereof al glossy layer of remoistemableV adhesive coating composition having as itsessential ingredient f polyvinyl alcohol which has been boiled in aqueous solution for a time sufficient to give it a lustrous, structurally stabilized, integrated, homogenized, quicker adherent, nonjelling andjfreeffiowingLwhile in cooled solution,lmo,r e resistant to humidity, more responsive to appliedrnoisture,

clearer, smoother, stronger, and more exible lmforming, and quicker-drying, character.

7. The article claimed in claim 6 wherein said paper comprises a postage stamp.

8. The article claimed in claim 6 wherein said paper comprises a label.

9. The article claimed in claim 6 wherein said paper comprises a gummed tape.

10. The article claimed in claim 6 wherein cane sugar has been added to the hot aqueous solution of polyvinyl alcohol at the conclusion of said boiling.

References Cited in the file of this patent UNITED STATES PATENTS 1,449,792 Swift Mar. 27, 1923 2,135,075 Hermann Nov. 1, 1938 2,162,618 Izard Iune 13, 1939 OTHER REFERENCES Du Pont Technical Data Bulletin 1-1043, PVA Elec- 5 trochemicals Dept., E. I. du Pont de Nemours & Co.,

filed U. S. Patent Oice Nov. 13, 1943.

Del Monte: Technology of Adhesives, 1947, pages 127, 128, 140. 

2. AN ENVELOPE HAVING ON THE UNDERSIDE OF THE MARGINAL PORTIONS OF THE SEAL FLAP THEREOF A GLOSSY LAYER REMOISTENABLE ADHESIVE COATING COMPOSITION HAVING AS ITS ESSENTIAL INGREDIENT POLYVINYL ALCOHOL WHICH HAS BEEN BOILED IN AQUEOUS SOLUTION FOR APPROXIMATELY ONE HOUR AND UNTIL ALL THE LAMPS HAVE DISAPEARED AND A NEAR-CLEAN HOMOGENEOUS SOLUTION HAS BEEN FORMED, WITH ALL VOLATILE CONTAMINANTS DISTILLED OFF THEREFROM. 